Electric switch



. ELECTRIC SWITCH Original Filed Nov. 6, 1941 3 Sheets-Sheet l Sept. 17,1946. F. G. LOGAN 2,4 7,71

ELECTRIC SWITCH Original Filed Nov. 6, 1941 3 Sheets-Sheet 2 a a if 571fjzgwg gw 30 Sept. 17, 1946. I LOGAN- 2,407,710

ELECTRIC SWITCH Original Filed Nov. 6, 1941 3 Sheets-Sheet 3 PatentedSept. 17, 1946 ELECTRIC SWITCH Frank G. Logan, Mount Vernon, N. Y.,assignor to Ward Leonard Electric Company, a corporation of New YorkOriginal application November 6, 1941, Serial No. 417,990, now PatentNo. 2,378,022, dated June 12, 1945. Divided and this application March27, 1943, Serial No. 480,767

4 Claims. 1

This invention relates to electric switches adapted for general use andfor control purposes and is of the magnetically operated contacting typealthough certain features of this improvement are applicable to othertypes of switches. Certain of the improvements disclosed herein and notclaimed are the inventions of George M. Stapleton and are described andclaimed in his pending United States application Serial No. 420,327,filed November 25, 1941, now Patent No. 2,378,162, issued June 12, 1945.

This application is a division of my pending original application SerialNo. 417,990, filed November 6, 1941, now Patent No. 2,378,022, issuedJune 12, 1945.

The general object of the improvements described and claimed herein areto produce an improved switch which is of compact form and ofcomparatively large current and rupturing capacity, and which will bedurable and dependable under long continued use. A particular object isto provide an improved form of arc chambers and relationship to thecontacts for effectively quenching the arc and occupying small space.This is accomplished in general by providing arc chambers whichindividually encircle the contacts in comparatively close proximitythereto and by mounting them so as to be movable with the movablecontacts of the switch. The improved construction permits the arcchambers to be made of light weight and of a sturdy form of structurethat will effectively cool and quench the arc and permit the effectivecarrying away of the hot gases upwardly in their natural tendency torise. The permissible proximity of the arc chambers to the contacts hasthe advantage of rapidly cooling the arc and heated gases and by reasonof the fact that the chambers are movable 'with the movable contacts,there rises the advantage of exposing fresh arc barrier surfaces to theare continuously during the opening movement of the contacts. Also,during the opening movement provision is made not only for the escape ofhot gases upwardly but for providing free access of air to the bottom ofthe chambers so as to permit a free and enforced movement of the hotgases upwardly and permit them to escape through the top of the arcchambers to the outside atmosphere. The free upward passage of the hotgases is facilitated further by cutting away the lower parts of the arcchambers to permit free inward passage of air upwardly through thechambers and these cut-away portions of the chambers also permitentrance of the supports for the movable contacts while maintainingample provision of arc quenching and cooling surfaces within the arcchambers; and the relationship of the parts is such that the arc iselectromagnetically forced against the walls of the chambers which areopposite the cut-away portions which insures the effective cooling andquenching of the arcs by the arc barrier surfaces on the opposite sideof the chambers from the cut-away portions. The are chambers or shieldsare preferably made of metal as such material can effectively withstandthe heating effects of the arcs without objectionable deterioration andthe high thermal conductivity of metal assists in the cooling of the arcand the heated gases. Either magnetic material, such as iron or sheetsteel, may be used for the arc chambers but nonmagnetic material, suchas brass likewise may be used. Also, the chambers may be made of othersuitable material than metal which is adapted to effectively withstandthe eflects of the arcs and hot gases without objectionabledeterioration of the exposed surfaces.

Other objects and advantages of this invention will be understood fromthe following description and accompanying drawings which illustrate oneembodiment of the invention.

Fig. 1 is a vertical central section in a plane at right-angles to theback of the switch; Fig. 2 is a top plan view with the connectingterminals shown in section; Fig. 3 is a horizontal section on the line33 of Fig. 1; Fig. 4 is a horizontal section on the line 4-4 of Fig. 1;Fig. 5 is an enlarged side view, partly in section, of one of the fixedcontacts; Fig. 6 is an enlarged perspective view of one of the arcchambers or shields; Fig. 7 is a vertical section on the line 1-1 ofFig. l; and Fig. 8 is a horizontal section on the line 88 of Fig. 7.

The apparatus is supported by a frame or base of sheet metal having ageneral U-shaped form..

The base of the U extends vertically and the two side portions extendforwardly from the base portion. The rear portion of the frame iscorrugated for strength, the projecting ribs Ia which extend verticallyalong the back, being forced forwardly from the metal sheet before it iscut and bent to the desired form. At about the middle of the backportion, two of the ribs la are further pressed forwardly formingprojecting ribs lb, as shown in Figs. 1 and 4, for a purpose laterexplained. The back portion is provided with openings Ic at the top andbottom, as shown in Figs. 1 and 7, for the purpose of securing the frameto a upporting panel. The forwardly extending side portions Id areprovided parts with a number of openings to as shown in Figs. 7 and 8for the purpose of ventilation and accessibility during assembly, and inrepair or adjustment of the parts. A number of projecting portionsextend from the side portions and are bent inwardly at right-angles atthe front of the frame for forming support for various parts. A pair ofthese projections if, shoWn in Figs. 1 and 2, forms a support for afront plate 2 which may be utilized for supporting auxiliary conti. o1apparatus or parts and also serves another function to be describedlater. The plate is also secured to a pair of inwardly turnedprojections lg of the frame which extend vertically along considerableportion of the frame. A pair of similar projections lh are positionedbelow the projections lg, as shown in Fig. l, and serves, together withthe projections lg, to support another front plate 3 which may beutilized for sup porting auxiliary control apparatus or parts. A pair ofsimilar projections it from the frame are positioned below theprojections lh and serve to support another plate the purpose of whichwill be later explained. The extensions lg carry at their upper middleportions a pair of projec'- tions i7", as shown in Figs. and 3, whichare curved inwardly and outwardly and serve a purpose later explained.They are opposite the pro-- jections lb of the rear portion of theframe. The main frame and its various extensions and projections notonly serve for supporting various parts but also accomplish otherobjects, as later described.

In describing construction of the switch and the relationship andoperation of its parts, the upper portion will first be described andthe description continued by reference to the other in progressive stepsdownwardly. The fixed contacts and inter-connections thereto aresupported by a block 5 of insulating material molded to the desiredform. It extends horizontally across the upper portion of the switch andis supported at its sides by resting upon the side portions id of theframe, as shown in Fig. 7 and upon the front projection if as shown inFigs, 1 and 2. The front tie plate 1! is provided at its upper part witha pair of inwardly extending projections 2a which extend over the frontedge of the insulating block 5 and thereby serves .to hold the frontportion of the block in fixed position. The rear portion of the block 5is held in place by a cross-pin t which extends over the rear part ofthe block, as shown in Fig. 1. This pin extends through slots tic in theside portions of the frame. The outer ends of the pins are formed withcircumferential grooves which are engaged by spring clips 6a, as shownin Fig. 2, for preventing endwise movement of the pin. When it isdesired to remove the block 5, it is merely necessary to remove one ofthe Clips 611 and then move the pin 6 endwise a short distance so as toclear the inside of a side portion of the frame and then by raising thefree end of the pin and after removing the other clip 6a, the pin can bewithdrawn from the other side of the frame. The slots lk permit thistilting and their final removal from either side of the frame as may bedesired. Of course, the pin may be removed by pulling it outlongitudinally after removing one of the pins 6a but where a number ofthese switches are stacked side by side closely in a row, the abovedescribed tilting method of removal of the pin can be accomplished eventhough another switch is mounted closely on each side. After removal ofthe pin the rear end of the block 5 is free to be raised from the frameand thus permit the front edge of the block to be withdrawn from underthe clamping extensions 2a. Thus the insulating block 5 may be readilyremoved and replaced, together with the parts carried by it, forinspection, cleaning or adjustment of the parts.

The block or head 5 is provided on its upper surface with ribs So, aswell shown in Fig. 7, which extend from front to back and also anupwardly extending rear cross-rib lib, as shown in Fig. 1. These ribsare for the purpose of strengthening the block and for also separatingthe upper portions of the fixed contacts which portions lie in thevalleys between the ribs. The fixed contacts are in the form ofdownwardly extending metal rods 7, the lower ends of which form thecontacting faces of the fixed contacts which faces are preferablyformed. of silver, or alloys of silver, or other suitable material, forobtaining good contact surfaces. The upper ends of the contact rods orcylinders l are of reduced diameter and project upwardly throughopenings in the head 5, being secured to the head by washers and nutsla. on the upper threaded ends of the contact rods. The upper ends ofthe contact rods are slotted so that they may be held b a screwdriverfrom turning while th clamping nuts la are turned tightly for lockingthe parts in fixed position. The lower portion of each fixed contact rodis encircled somewhat above its lower end by a ring 8 of insulatingmaterial, as shown in Fig. l and more particularly in Fig. 5. Thisinsulating ring may be secured to the rod in any suitable manner but, asshown in Fig. 5, is held in place by spinning or upsetting a portion ofthe metal rod 1, as shown in Fig, 5, against the upper and lower inneredges of the insulating ring. This ring acts as a Spacer on each fixedcontact for preventing engagement with adjoining parts and likewise as abarrier, although permitting free escape of the gases upwardly aroundits outer rim. In the particular switch shown, there are twelve fixedcontacts 1 in three rows of four each. The front and rear contacts ofeach row are adapted to be connected to the controlled circuit, orcircuits, by terminal connections in the form of flat strips 81) whichare bent to extend under the clamping nuts la and locking washers on thecontact posts and are provided at their outer ends with screws 8a andlocking washers for receiving the conducting leads. The inner twocontact posts of each row are connected by a metal link 9 which lies onthe top of the contact head and extends under the clamping nuts 1a andwashers of the two contact posts. The two front contact posts of eachrow are adapted to be bridged by a movable contactor, as indicated inFig. l, and the two rear contact posts of each row are adapted to bebridged by a contactor. Thus the circuit may be traced from the outerterminal 8a of one row through the front contact post and bridgingcontactor to the second contact post and then through the link 9 to thenext contact post and thence through the rear bridging contactor to therear contact post and rear terminal 8a. When the circuit of each row isopened there are thus secured four breaks in the circuit in series witheach other which tends to reduce the arcing at each contact. Theprovision of the terminals affords means for connecting the switch inany way desired to the outside circuit and by locating the links 9 atthe top of the insulating head, they are conveniently accessible andremovable if desired for replacement by the connection of overloadcontrolling devices between the inner terminals of the different rows,or by the connection of ammeters or other devices for particularpurposes.

The movable contact assembly is formed of two separable blocks of moldedinsulating material which are securely clamped together for holding thevarious associated parts in place. The lower insulating block it extendshorizontally between the side portions of the frame. The upper block I lsimilarly extends horizontally between the side portions of the frameand is removably secured to the lower block by screws l2, well shown inFigs. 3 and '7, which pass vertically down through the upper block andlower block and have a threaded engagement at their lower ends with achannel shaped sheet metal strip [3 to be later described. The lowerinsulating block in is provided with a number of vertical openings lilaeach of which is below and opposite the previously described fixedcontacts. These openings are for the purpose of providing a free flow ofair upwardly to and beyond the contacts to aid in extinguishing the arcsand in carrying away the hot gases. The upper block H of the movableassembly is provided with twelve cylindrical openings I la which areopposite the contact posts I and these openings extend verticallydownward and communicate with the openings Ida in the lower block It],as well shown in Figs. 1 and '7.

A cylindrical arc shield or barrier i4 is positioned within each of theopenings i la and each of these shields extend upwardly above the blockII a short distance and the upper end of each shield surrounds theinsulating ring 8 but is spaced therefrom to permit the free escape ofgases upwardly between the shield and the insulating ring. The lowerportion of each shield is cut away at Ma on one side, as particularlyshown in Fig. 6 and'a space Mb is left between the edges of the upperportion of the shield. The lower portion of the shield is flaredoutwardly at 14c and, as well shown in Fig. l, the adjoining portions ofthe insulating blocks Ill and I I are shaped to receive these flaredportions of the shields so that when the two insulating blocks areclamped together by the screws l2, the shields I i will be held in fixedposition. Provision is also made for insuring that the shields aremaintained in their proper positions with reference to the movablecontacts. This is accomplished by forming vertical projections Ilb onthe insulating block II which project within the openings Ha, as shownin Fig. 3. The width of each projection llb corresponds with the openingMb of each shield and when the shield is passed into its opening in theinsulating block, the vertical edges of the upper portion of the shieldwill engage the projection l lb and thereby insure that each shield ismaintained in its proper position. The barriers or shields [4 may beformed of sheet metal and it should be noted that each of these shieldsis individually insulated from other portions of the apparatus. Metalshields are desirable owing to their ability to resist objectionabledisintegration from effects of arcs; and either magnetic or nonmagneticmetal may be used, such as iron or brass but the shields may be made ofmaterial other than metal which will retain its form and be capable ofwithstanding the eifects of the arcs.

Each of the movable contacts bridges a pair of fixed contacts, as shownin Fig. 1, and is in the form of a sheet metal channel piece l5, as wellshown in Fig. '7 and is preferably made of copper; and this channelpiece carries at each end a contact [50; which is securely fastened tothe piece 15 as by riveting or otherwise. These contacts are preferablyformed with a face of silver or silver alloy for insuring good contactwith the fixed contacts when engaging them. Each of these bridgingmovable contact assemblies extends through the cut-away portions Ma of apair of shields so that the contact faces are centrally positionedwithin the shields and opposite a pair of fixed contacts, as shown inFig. 1. Each bridging contact is kept in proper alignment by a contactguide [6 in the form of a metal strip of rectangular form, as shown inFigs. 1 and 3. The lower end of each of these guiding strips is knurledor roughened and is forced into an opening in the insulating block In soas to be firmly retained in position by the block Ill. The stripsare'secured in position in the block in before the block II is fastenedthereto; and the openings formed in the insulating block I l forreception of the upper ends of these strips are of sufficient size tofreely receive the upper ends of the strips in assembling the parts.Each bridging piece ii of the movable contacts is provided with acentral slot of the same form as the cross section of the strip and isadapted to freely move along the guiding strip. A spring I! encircleseach guiding strip l6 and one end of the spring is positioned below eachof the bridging pieces 15 while the other end seats in an opening formedin the insulating block l0.

The movable contact assembly, as previously described is composed of twoseparable blocks of molded insulation fastened together and they supportand carry the arc barriers or shields as well as the spring pressedbridging contacts. The fastening screws 12 serves as a common means, notonly for holding the insulating blocks it and H together, but byengaging the metal piece iii of U form, serve to hold all parts of themovable contact head together.

The parts are shown in the open position of the sWitch and when the parti3 is moved upwardly upon the energization of the magnet, the movablecontact assembly including the arc chambers or shields i i, is movedupwardly and thereby cause the bridging movable contacts to engage theirrespective pairs of fixed contacts 1. After initial engagement and uponfurther upward movement of the parts, the movable bridging contacts areforced downwardly by their engagement with the fixed contacts along theguiding strips to against the pressure of the springs 11. As thebridging contacts have a certain freedom of movement on the guidingstrips, they are self -adjusting so that the pressure of the movablecontacts against the fixed contacts is equalized, thereby insuringproper engagement and sufficient contact pressure of each movablecontact with its fixed contact. Also, by reason of the movable contactassembly being pivotally connected, as hereinafter explained with theactuated portion of the magnet, the movable contact head is capable ofmovement as a whole 50 as to be self-adjusting in relation to the fixedcontacts in order to further insure equalization of contact pressure inall parts.

When the magnet is deenergized for opening the switch, the pressure ofthe contacts and the springs I1 together with the weight of the parts,force the movable contact head downwardly with a quick opening movement.In this opening action the arc barriers are, of course, moved downwardlywith the movable contact head and this action results inconstantlybringing fresh sur faces of the. shields oppositethe arcs and therebyaid .in-coolingand. extinguishing'them. .Furthermore, by bringing newsurfaces opposite the arcs, the arc. chambers are lesssubject.todeterloration from effects .ofthearcs, as compared with fixed arcbarrierswherethe arcing effects are concentratedon the same portions ofthebarriers. .Also, the .fre spaces betweenthe arc chambers and thefixedcontacts and aroun'dthe insulating rings 8 provide open passagesfor-the. free flow of the hot. gases upwardlyin their natural tendencyof movement and out through the top of the chambers, this free. passageof thechot gases upwardly and outwardly being assisted by the freeinflowof air through the openings 10a below each of the contacts. Theare chambers also serve to-cool the hotgases as they pass freelyupwardly and out from the chambers. The cut-awayportions of the chambersfor thepurpose of permitting the introduction of the movable contactsand f the bridging elements carrying them, do not lessen theeffectiveness of the structure in extinguishing the arcs because, withreference .to each, pair of. contacts, the current passes through a loopformed by one fixed contact, the bridging contacts and the other fixedcontact which results in forcing the arcs outwardly from the loop alwaysagainst the portions of the chambers which are not cut away. Thecut-away portions of. the chambers serve also to facilitate the inwardpassage of air to the chambers to aid in the upward and .outward passageof the hot .gases through the chambers.

The function of the inwardly pressed projections 11) from the rear ofthe main frame and of the projections I? at the front :portion of theframe on opposite ends of the movable contact head is for restrainingthernovement of the head under shocks and jars. The movable head isnormally guided in its movement by parts hereinafter described but theprojecting portions referred to serve as restraining means unde unusualor severeconditions for preventing the movable head being jolted to anabnormal position, as one of the; purposes of this'improved switch isfor adaptation to withstand severe shocks and jars as, for example, whenused on naval vessels.

The magnet core actuating the switch to closed position is composed oftwo similar laminated parts and on account of the fact that the partcorresponding tothe usual fixed part is movable for-the purpose ofsecuring self-alignment and self-adjustment, it will be referred toherein as th non-actuated part of the magnet and the other-partas'the-actuated part of the-magnet. Each part-is built up of laminationsof general E-form'and'the laminae of each part are of the same size-andshape which simplifies the stocking problem and the cost of assembly.The faces ofthe ends of the three legs ofthe E are ground,afterassemblyof the core parts, to lie in thesame plane; and-whenthelparts arein their attracted position, there is no air gap betweenthe engaging faces-of the core portions. This not only simplifies thecost ofnianufacture by permitting the grinding of the engaging faces byone operation in the same plane but the omission of any air gap resultsin the advantages of lower'voltampere input to the magnet coil,uniformity of coil inductance and a slight time delay before actuationof the switch to open position, due to higher residual magnetization andhigher induced-secondary currents in the iron core, the last namedadvantage being particularlydesirable in overcoming the opening of theswitchwhen the circuit of .the magnet coil is momentarily 8 openedat'auxiliary .control contacts by severe shocks on the apparatus.

Referring to Fig. l, the three-legged-form of the laminae E8 of thenon-actuated portion of the magnetis shown as having the legs extendingvertically downward and the three-legged laminae l9 of 'the actuatedportion of themagnet is shownwith :its legs extending upwardly and,asalready explained, the engagingfacesof the legs are ground, afterassembly,;in the same plane so as to insure uniform, good surfacecontact. The end plates 18a of the non-actuated portion ofthe magnetcore are shown inFig. .4 asprovided at each end with angular extensionslGb which project .rearyvardly and forwardly. These extensionsrespectively engage sheet metal brackets 2i! which. are bent toadesiredishapaas shown, andprovidedwith side portions-Ha ley whichitheyare securely fastened to the side portions of the main frame by the.screws'ZlJb. The projections 132) from .the end plates loosely engagevertical Slots .230 in the cross brackets :20 so ..as.to permitconsiderable freedom of movement. of the.noneactuatedrportion.of themagnet in all directions for the purposeof self-adjustment, as laterexplained, but .is, of course,:restrained by the slots from assumingextreme-or abnormal positions. :In assembling'the core oftl'ie.=non-actuated.portion of the-magnetythe end plates lflcz havingthe .projections 18b :are .permanently fastened to the laminae, .as byriveting, andthe pole faces afterwards ground. This eliminates possible.clistortionofthe parts which might occur if the end plates or theirsupporting extensions were attachedaitcr grinding. The magnet coil 2| iscarried by aispool Zia of-insulating material and is held in.place,1asshown in Fig. .7 by a U-shaped strip 25 of metaL'the .base of .the Upassing over the top of the laminae l8 and the legs extending downwardlyinside-the magnet'coil. The supporting strip 23 isprovided withoutwardly extending projections 23a at the lower ends of the legs whichpass under and supportthe magneticoil.

Tlhev actuated portion of the .magnet. comprising the laminae l 9isprovided with end plates l9a which extend along. eppositesides of thelaminae andiare bent. at right-angles, as shownin. Fig. 8, to' passinwardly overtheends of thelaminae and again bent: outwardly:atright-angles to formextensions I'Sb. These end extensions are spacedfrom each other for :receiving the driving rods Ztwhich latterare'connected vfor actuation of the. movable. contact head. At thezfrontportions of the end plates lfla issecured a pair of angular pieces25which are bent at right-angles sa es to extend toward ithesideportions of the main frame as shown'in Fig. 8. Innassembling the corestructure of theactuated-part of the magnet, theend plates L911 and theangular pieces 25 are permanently fastened together and tothelaminaeasbyriveting theparts, after which the pole faces .:of thisportion of the magnet are ground in a single operationin'thesame plane.This avoids possiblefdistortion. of this portion of the magnet which:otherwise might .occur if the end platesor pieces 25 werezattached tothe laminae after the grinding. operation.

There are :two driverroids 24, .one in :the back and oneinithefrontportion'of the'apparatus, for connecting .the. actuated :portion of the.magnet with the movable contacthead. 'These rods areof square "crosssection, .as shown in Fig. .4, andare pivotally connected by pin 24a.between the extensions r Nb :of theendsplates as :showniin Fig. 8. Thedrive rods extend upwardly from these pivotal connections and areloosely guided in their movement by the two brackets Zil, as shown inFig. 4, these brackets being bent at their middle portions to formvertical guiding channels for the rods. The upper end of the rods areriveted, or otherwise firmly secured to the ends of metal strip or yoke26 of channel form, the bent side portions extending upwardly, as shownin Fig. 7. These side portions fit freely within the downwardlyextending side portions of the strip or yoke [3 which has beenpreviously described as being fixed to the movable contact head by thescrews E2. The two yoke pieces are pivotally connected together at theirmiddle portions by a pin 21, as shown in Figs. 1 and '7.

Thus the actuated portion of the magnet is not only pivotally connectedto the drive rods but there is also a pivotal connection between theyoke of the drive rods and the yoke of the movable contact head. Thisgives a flexibility of movement between the parts and provides for theself-adjustment and alignment of the parts for insuring the properseating of the magnet and aids in the proper seating and balancing ofpressure of the contacts. The axes of these pivotal connections are atrightangles to the side plates of the main frame and to the bridgingmovable contacts for permitjting self-adjustment of the parts in planeperpendicular to the back portion of the main frame; and the slightlooseness of the connections permits sufficient freedom of movement foradjustment in the direction of planes parallel to the 3 back portion ofthe main frame.

Also, instead of providing a heavy main supporting frame in the attemptto secure rigidity of the non-actuated part of the magnet in a fixedposition, the non-actuated part of the magnet is mounted, as alreadydescribed, so as to be movable with reference to the supporting frameand movable with reference to other parts of the switch for securingproper alignment and engagement of the parts by self-adjustment. Thisavoids the time and expense otherwise required to machine the parts toclose clearances and likewise avoids the time and care required inmaking refined adjustments after the assembly of the parts. Furthermorein the prior rigid and attempted perfectly aligned structures, the

alignment is not permanent, especially when subjected to severe shocks,owing to the distortion of the parts which inevitably follows pronouncedshocks and jars. In the present form of construction the free floatingand self-adjustment of the parts with reference to each other insurespermanent and proper relationship of the parts which is not affected bydistortion of the main support or other parts of the apparatus.Moreover, with this improved structure the proper seating andself-alignment of the parts give continued quiet operation whenenergized and in fact becomes more quiet with continued use owing tocontinued improvement in the surface engagement of the parts the longerthe switch is used.

In assembling this improved structure, the parts are connected togetheras described except that the screws Ziib which hold the cross-brackets2!! to the main frame are left to loosely engage the parts until afterthe magnet is energized when the screws 29b are tightened up graduallyin succession a little at a time until they are all uniformly tight. Inthis manner the best relaof the pole faces tive position of the parts issecured for insuring a uniform and balanced engagement of the parts inproper alignment and insures a minimum noise level in later use afterthe magnet is energized.

The usual lag loop or coil is provided within the faces of one or morepoles of the magnet and in the present structure this is preferably inthe form of a rectangular copper loop 28, as shown in plan view in Fig.8 and held in place by upsetting portions of the edges of the lalninaeover the loop. As shown in Fig. 1, one of these lag loops is provided onthe outer pole face of the nonactuated portion of the magnet, while theother of the lag loops is provided on the face of the inner pole of theactuated portion of the magnet. This relative arrangement insures thatat least one of the two engaging faces of each pole of the magnet willbe a solid, smooth face and thereby avoid distortion or unevenness ofthe pole faces under continued use. These lag loops are applied to andsecured in place on the two portions of the magnet before the finalgrinding operation of the pole faces.

Special additional provision is made for pre venting undesired openingor closing of the switch when subjected to severe vertical shocks or tovertical components of shocks. This is accomplished by the pro-vision ofinertia controlled latches, the operation of which is dependent uponchang of motion of the entire structure. One of the latches is forpreventing the switch from closing under severe shocks and the other isfor preventing the switch from opening under severe shocks. One of theseinertia latches is shown in the lower right-hand portion of Fig. 1. Itcomprises a weighted body portion 29 which extends across the lowerfront portion of the main frame, as shown in Fig. 8, and is providedWith a latch 29a at each end which eXtends upwardly and is provided withan inwardly rojecting hooked end. These two ends of the latches arenormally positioned, as shown in Fig. 1, somewhat above and in front ofthe angular pieces 25 secured to the actuated portion of the magnetcore. The two latches are pivoted on a pin 3%! which is supported at itsends in the side portions of the main frame. The weighted portion 25! ofthe latch being positioned outwardly from the pin 3%, tends to maintainthe latches in the position shown in Fig. 1 out of engagement with theangular pieces 25. An adjustable screw 3! mountedon the tie-plate 4limits the outward movement of the latches. The radius from the axis ofthe pin 33 to the center of gravityof the mass 29 is shorter than thedistancefrom the axis of the pin 30 to the hooked ends of the latches.It follows that any movement of the mass 29 about its pivot is amplifiedin the movement of the hooked end of the latch in proportion to theirrelative distances from the pivot pin. Under normal conditions thelatches are out of engagement with the angular pieces 25 and thusenergizing of the magnet coil will permit the switch to be closed in themanner already described. But if the switch is in the open position andthe apparatus is subjected to a severe vertical shock, or to thevertical component of such a -shock, the actuated portions of the switchmight move with relation to the fixed contacts and result in anundesired closing of the switch. However, before this can occur, themass 29 will move upwardly and by the amplification of movement referredto, the hooked ends of the latches will be rapidly moved inwardly andengage the a gular pieces 25 before the switch can close and therebyrestrain and prevent the closing of the switch. After the passing of theshock the inertia latch will fall to its normalposition so that theswitch will be free to close upon energization of its'magnet.

A similar inertia latch or stop prevents the undesired opening of theswitch under severe vertical shocks by a reverse manner of operation. Amass 32 is positioned at the lower central portion of the switch, asshown in Fig. l, and extends crosswise between the side portions of themain frame. The mass is provided near its ends with supporting plates32a which are pivotally mounted upon a; pin 33. which extends. betweenand is supportedby theside DOl'tlOI'lSzOf the mainframe. Between; theextensions 32a. is..a cross-bar 32b, theupper portion of. whichisnotchedat 3.20. A spring, is connected. at oneendtotheweight 32 and at itsother: end'to the. pin 30 for normally holding this shockpreventing-means. in the position shown in Fig. 1. The mass 32' isprovided with extensions 3211 as. shown in Fig. 7 which normally engagethe lower edges of the side portions of the main frame for limiting theupward movement of. the restraining means to the; position shown inFig. 1. When the switch isclosed, the. lower inside corner of theactuated portion of the core is positioned opposite and above thenotch320 of the inertia latch. When the apparatus is subjected to shock, .orto avertical component thereof, when the switch isclosed, the opening ofthe switch is prevented because any tendency to open the switch willcause the' mass. 32 to move downwardly and due to the amplified relativemovement of the notch 320 by reasons of its distance from its axis fromthe pin 33 being greater than the distance from its aXis'to the centerof gravity of the mass 32, the notched portion 320 will move underthelower inside corner of the actuated core portion of the switchbeforethe switch has had time to open. This action will prevent the opening ofthe switch until the full eifects of the shock or shocks have passed,after which the spring 34 will move the restraining means to the normalposition shown in Fig; 1 where it will permit the normal opening of theswitch when desired.

Although a particular embodiment of this improvement has been shown anddescribed; various modifications may be adaptation to particularrequirements without departing from thescope of the invention.

I claim:

1. An electric switch comprising afixed insulating support, a contactcarried thereby and extending downwardly therefrom, a vertically movableinsulating support below said fixed contact, a contact carried by saidmovable insulatingsupport and adapted to engage said first named contactupon the upward movement of said movable insulating support, avertically extending arc shield surrounding and. spaced from saidcontacts throughout the length of the shield and fixed at its lower end.to said movable insulating support and having openings at both of itsends, said movable support having an opening opposite the lower end ofsaidarc shield for the free passage of gasestherethrough and upwardthrough the space between the arc shield and the contacts forextinguishing the are upon the opening of the switch, and the downwardmovement of said insulating support and of said are shield exposingfreshsurfaces of the interior of said are shield to the elfectsof the arcduring the/sepa ration of the contacts in the opening movement.

a severe vertical i made therein for 2 .'An electric switch comprisingafixed insulating support, a contact carried thereby and .extendingdownwardly therefrom, a vertically movable insulating support below saidfixed contact, a contact carried by said movable insulating'support andadapted to engage said first named contact upon the upward movement ofsaid movabl insulating support, a vertically extending arc shield ofmetal surrounding and spaced from said contacts throughout the length ofthe shield and fixed at its lower end to and insulated by said movableinsulating support and having openings at both of its ends, said movablesupport having an opening opposite the lower end of said are shield forthe free passage of gases therethrough and. upward through the spacebetween. the arc shield and the contacts for extinguishing the arc uponthe opening of the switch, and thedownward movement of said insulatingsupport and of said arc shield exposing fresh surfaces oflil'llilllterior of said are shield to the effects oi the arc during-theseparation of the contacts in the opening movement.

3. An electric switch comprising a fixed insulating support, a pair ol-contacts carried thereby and extending downwardly therefrom, a movableinsulating support, a pair of contacts connected by a bridge and carriedby the movable insulating support for engaging the first named pair ofcontacts respectively upon the upward movement of the movable insulatingsupport, a pair of arc shields carried by said movable insulatingsupport, each of said shields having a top opening, said shieldssurrounding each pair of the engaging contacts respectively and spacedtherefrom throughout the length of each shield for providing anintervening air space between the shields and the contacts forpermitting the free passage of gases from the arc therethrough, each ofsaid shields having a side opening opposite the side opening of theother shield for receiving the bridge connection of said second pair ofcontacts and for permitting the free passage of air to the shields andaround the contacts and through said top openings for extinguishing.the. are upon the opening of they switch, and means for actuating saidmovable insulating support for. closing and opening the switch and forexposing fresh surfaces of the interior of said are shields to theeffects'of the arc during the separation of the engaging contacts. bythe-downward movement of said movable. insulating support in opening theswitch.

4.. An electric switch comprising a fixed'insulating support, a pair ofcontacts carried thereby and extending downwardly therefrom, a movableinsulating support, a pair of contacts connected by a bridge and carriedby the movable insulating support for engaging the first named pair ofcontacts respectively upon the upward movement of the movable insulatingsupport, a pair of are shields of metal carried by-said movableinsulating support and insulated thereby, each of said shields having atop opening, said. shields. surrounding each pair of the engagingcontacts respectively and spaced therefrom throughout the length. ofeach shield for providing an intervening. air space between. the shieldsand the contacts. for permitting the free passage of gases from the arctherethrough, eachofsaid shields having a side opening opposite the sideopening of the other shield for. receiving the bridge cone nection ofsaid. second pair of contacts and for 13 permitting the free passage ofair to the shields and around the contacts and through said top openingsfor extinguishing the are upon the opening of the switch, and means foractuating said movable insulating support for closing and opening theswitch and for exposing fresh surfaces of the interior of said areshields to the effects of the arc during the separation of the engagingcontacts by the downward movement of said movable insulating support inopening the switch.

FRANK G. LOGAN.

